Complement C1s subcomponent (activated) (C1s)

Complement C1s subcomponent (activated) is a serine protease that forms part of the C1 complex, the first component initiating the classical pathway of the complement system[1][3][6]. In its active form, C1s cleaves complement proteins C4 and C2, leading to the assembly of C3 convertase and propagation of the complement cascade. The classical complement pathway facilitates pathogen clearance, opsonization, and regulation of immune complexes. Dysregulation or aberrant activation of C1s is implicated in various autoimmune diseases, infections, and some cancers. C1s, together with C1r and C1q, comprises the C1 complex; its activation is a therapeutic target, and inhibitors such as monoclonal antibodies (e.g., sutimlimab) are being developed and used clinically[6]. Safety challenges include potential immunosuppression and increased infection risk when C1s function is blocked[6].

Other names

complement component 1 subcomponent sC1sactive C1scomplement C1s serine protease

Inhibition of serine protease activity Blockade of C4 and C2 cleavage to prevent downstream complement activation